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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html> <head> <title>Using Register Globals</title> <meta http-equiv="content-type" content="text/html; charset=UTF-8"> </head> <body><div style="text-align: center;"> <div class="prev" style="text-align: left; float: left;"><a href="security.errors.html">Error Reporting</a></div> <div class="next" style="text-align: right; float: right;"><a href="security.variables.html">User Submitted Data</a></div> <div class="up"><a href="security.html">Security</a></div> <div class="home"><a href="index.html">PHP Manual</a></div></div><hr /><div> <h1>Using Register Globals</h1> <div class="warning"><b class="warning">Warning</b><p class="simpara">This feature has been<em class="emphasis">DEPRECATED</em> and <em class="emphasis">REMOVED</em> as of PHP 6.0.0.Relying on this feature is highly discouraged.</p></div> <p class="para"> Perhaps the most controversial change in PHP is when the default value for the PHP directive <a href="ini.core.html#ini.register-globals" class="link"> register_globals</a> went from ON to OFF in PHP <a href="http://www.php.net/releases/4_2_0.php" class="link external">» 4.2.0</a>. Reliance on this directive was quite common and many people didn't even know it existed and assumed it's just how PHP works. This page will explain how one can write insecure code with this directive but keep in mind that the directive itself isn't insecure but rather it's the misuse of it. </p> <p class="para"> When on, register_globals will inject your scripts with all sorts of variables, like request variables from HTML forms. This coupled with the fact that PHP doesn't require variable initialization means writing insecure code is that much easier. It was a difficult decision, but the PHP community decided to disable this directive by default. When on, people use variables yet really don't know for sure where they come from and can only assume. Internal variables that are defined in the script itself get mixed up with request data sent by users and disabling register_globals changes this. Let's demonstrate with an example misuse of register_globals: </p> <p class="para"> <div class="example"> <p><b>Example #1 Example misuse with register_globals = on</b></p> <div class="example-contents"><div class="phpcode"><code><span style="color: #000000"><span style="color: #0000BB"><?php<br /></span><span style="color: #FF8000">// define $authorized = true only if user is authenticated<br /></span><span style="color: #007700">if (</span><span style="color: #0000BB">authenticated_user</span><span style="color: #007700">()) {<br /> </span><span style="color: #0000BB">$authorized </span><span style="color: #007700">= </span><span style="color: #0000BB">true</span><span style="color: #007700">;<br />}<br /><br /></span><span style="color: #FF8000">// Because we didn't first initialize $authorized as false, this might be<br />// defined through register_globals, like from GET auth.php?authorized=1<br />// So, anyone can be seen as authenticated!<br /></span><span style="color: #007700">if (</span><span style="color: #0000BB">$authorized</span><span style="color: #007700">) {<br /> include </span><span style="color: #DD0000">"/highly/sensitive/data.php"</span><span style="color: #007700">;<br />}<br /></span><span style="color: #0000BB">?></span></span></code></div> </div> </div> </p> <p class="para"> When register_globals = on, our logic above may be compromised. When off, <var class="varname">$authorized</var> can't be set via request so it'll be fine, although it really is generally a good programming practice to initialize variables first. For example, in our example above we might have first done <i>$authorized = false</i>. Doing this first means our above code would work with register_globals on or off as users by default would be unauthorized. </p> <p class="para"> Another example is that of <a href="ref.session.html" class="link">sessions</a>. When register_globals = on, we could also use <var class="varname">$username</var> in our example below but again you must realize that <var class="varname">$username</var> could also come from other means, such as GET (through the URL). </p> <p class="para"> <div class="example"> <p><b>Example #2 Example use of sessions with register_globals on or off</b></p> <div class="example-contents"><div class="phpcode"><code><span style="color: #000000"><span style="color: #0000BB"><?php<br /></span><span style="color: #FF8000">// We wouldn't know where $username came from but do know $_SESSION is<br />// for session data<br /></span><span style="color: #007700">if (isset(</span><span style="color: #0000BB">$_SESSION</span><span style="color: #007700">[</span><span style="color: #DD0000">'username'</span><span style="color: #007700">])) {<br /><br /> echo </span><span style="color: #DD0000">"Hello <b>{$_SESSION['username']}</b>"</span><span style="color: #007700">;<br /><br />} else {<br /><br /> echo </span><span style="color: #DD0000">"Hello <b>Guest</b><br />"</span><span style="color: #007700">;<br /> echo </span><span style="color: #DD0000">"Would you like to login?"</span><span style="color: #007700">;<br /><br />}<br /></span><span style="color: #0000BB">?></span></span></code></div> </div> </div> </p> <p class="para"> It's even possible to take preventative measures to warn when forging is being attempted. If you know ahead of time exactly where a variable should be coming from, you can check to see if the submitted data is coming from an inappropriate kind of submission. While it doesn't guarantee that data has not been forged, it does require an attacker to guess the right kind of forging. If you don't care where the request data comes from, you can use <var class="varname"><a href="reserved.variables.request.html" class="classname">$_REQUEST</a></var> as it contains a mix of GET, POST and COOKIE data. See also the manual section on using <a href="language.variables.external.html" class="link">variables from external sources</a>. </p> <p class="para"> <div class="example"> <p><b>Example #3 Detecting simple variable poisoning</b></p> <div class="example-contents"><div class="phpcode"><code><span style="color: #000000"><span style="color: #0000BB"><?php<br /></span><span style="color: #007700">if (isset(</span><span style="color: #0000BB">$_COOKIE</span><span style="color: #007700">[</span><span style="color: #DD0000">'MAGIC_COOKIE'</span><span style="color: #007700">])) {<br /><br /> </span><span style="color: #FF8000">// MAGIC_COOKIE comes from a cookie.<br /> // Be sure to validate the cookie data!<br /><br /></span><span style="color: #007700">} elseif (isset(</span><span style="color: #0000BB">$_GET</span><span style="color: #007700">[</span><span style="color: #DD0000">'MAGIC_COOKIE'</span><span style="color: #007700">]) || isset(</span><span style="color: #0000BB">$_POST</span><span style="color: #007700">[</span><span style="color: #DD0000">'MAGIC_COOKIE'</span><span style="color: #007700">])) {<br /><br /> </span><span style="color: #0000BB">mail</span><span style="color: #007700">(</span><span style="color: #DD0000">"admin@example.com"</span><span style="color: #007700">, </span><span style="color: #DD0000">"Possible breakin attempt"</span><span style="color: #007700">, </span><span style="color: #0000BB">$_SERVER</span><span style="color: #007700">[</span><span style="color: #DD0000">'REMOTE_ADDR'</span><span style="color: #007700">]);<br /> echo </span><span style="color: #DD0000">"Security violation, admin has been alerted."</span><span style="color: #007700">;<br /> exit;<br /><br />} else {<br /><br /> </span><span style="color: #FF8000">// MAGIC_COOKIE isn't set through this REQUEST<br /><br /></span><span style="color: #007700">}<br /></span><span style="color: #0000BB">?></span></span></code></div> </div> </div> </p> <p class="para"> Of course, simply turning off register_globals does not mean your code is secure. For every piece of data that is submitted, it should also be checked in other ways. Always validate your user data and initialize your variables! To check for uninitialized variables you may turn up <a href="function.error-reporting.html" class="function">error_reporting()</a> to show <b><tt>E_NOTICE</tt></b> level errors. </p> <p class="para"> For information about emulating register_globals being On or Off, see this <a href="faq.misc.html#faq.misc.registerglobals" class="link">FAQ</a>. </p> <blockquote><p><b class="note">Note</b>: <b>Superglobals: availability note</b><br />Superglobal arrays such as <var class="varname"><a href="reserved.variables.get.html" class="classname">$_GET</a></var>,<var class="varname"><a href="reserved.variables.post.html" class="classname">$_POST</a></var>, and <var class="varname"><a href="reserved.variables.server.html" class="classname">$_SERVER</a></var>, etc. are availableas of PHP 4.1.0. For more information, read the manual section on<a href="language.variables.predefined.html" class="link">superglobals</a><br /></p></blockquote> </div><hr /><div style="text-align: center;"> <div class="prev" style="text-align: left; float: left;"><a href="security.errors.html">Error Reporting</a></div> <div class="next" style="text-align: right; float: right;"><a href="security.variables.html">User Submitted Data</a></div> <div class="up"><a href="security.html">Security</a></div> <div class="home"><a href="index.html">PHP Manual</a></div></div></body></html>⌨️ 快捷键说明
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